Lesson 4ª

 

 

 

 

 

   

 

WHOLE NUMBERS

Remember; we have just studied natural numbers and we learnt that they are whole. This means that they don't have decimals and that they are positive. But, what happens with negative numbers? There is also a group of numbers know as "negative numbers". For example, when we say it's –3ºC in Teurel. This means there are 3 degrees Celsius below zero.

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If you draw a vertical line and you find its centre, this would be "zero". Everything (value) above this would be positive. Anything below it would be negative. To add values, divide the line in equal parts and write the corresponding values (numbers).

If you trace a horizontal line going through "zero" over the vertical line we drew before and then we divide it in equal parts, we can represent whole numbers. Positive numbers would go to the right of "zero", and negative numbers would go to the left.

THE OPPOSITE OF A NUMBER: the opposite of a number is the one found on the other side of Zero and at the same distance from it. For example: 3 and -3

WHOLE NUMBERS IS A GROUP OF NUMBERS COMPOSED BY POSITIVE AND NEGATIVE NUMBERS AND ZERO.

IN OTHER WORDS, WHOLE NUMBERS ARE COMPOSED BY ALL NATURAL NEGATIVE NUMBERS AND ZERO.

The money you have in your pockets is positive. Any money you owe is negative.

Imagine you have 10 €  and you pay Charles the 4 € you owed him. This means you now have left:   10 – 4 = 6 €.

Lets say you owe Charles 15 €  and you have 10 €, you still owe him 5: 10 – 15 = - 5 €. 

ABSOLUTE VALUE OF A NUMBER: IS THE VALUE OF THE NUMBER WITHOUT TAKING INTO COSIDERATION ITS SIGN. To indicate the absolute value of any number, we write the number with its corresponding sign between bars:

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To add two numbers with the same sign: you add them and they keep the sign they have; positive (+) or negative (-):

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To add numbers with different signs, you subtract them and you add the sign of the highest number:

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Solve the following exercises:

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Up until now, we have worked with sums and subtractions. Lets see multiplying and dividing:

The product or quotient of two numbers with the same sign are always positive:

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